In machining processes, material is removed from a workpiece by a tool. The tool is advanced into the workpiece until it reaches a position where the workpiece is at its final finished size. For example, in abrasive or grinding machining processes, the material is removed by a large number of cutting points held in a friable matrix which may be in the form of a grinding wheel.
In existing machining processes, an operation to bring a portion of a workpiece to its final size is divided into a number of distinct, separate phases. Commonly, these phases may be denoted as “fast”, “medium” and “slow” feed operations. An example of process control in this way is illustrated in FIG. 8 of US 2014/0213147. Here, three grinding phases are denoted as “rough grinding”, “precise grinding” and “fine grinding”.
In these known grinding processes, the infeed parameters (such as the relative velocity between the tool and an axis about which the workpiece is rotating) are determined for each phase. This is with a view to achieving safe material removal whilst avoiding structural damage such as burn-related loss of hardness. The rate of material removal is set at a different level in each phase as the workpiece approaches size to minimise geometric errors. Each step therefore has a constant feed rate (or relative velocity) which is reduced from one step to the next during the approach of the wheel to the finished workpiece size.